[rrd-users] Adding two VDEF values together

[Alex van den Bogaerdt]

Thank you for letting me know how VDEF works.

----- Original Message ----- 
From: "Yannick Marquet" <itcsoft54 at yahoo.fr>
To: "Alex van den Bogaerdt" <alex at vandenbogaerdt.nl>
Cc: <rrd-users at lists.oetiker.ch>
Sent: Saturday, February 23, 2013 2:12 PM
Subject: Re: [rrd-users] Adding two VDEF values together


> Hello,
>>> So, a VDEF is a set of data and a CDEF is a single value, but a TOTAL
>>> will be a single value?
> no, it is opposite :
> http://oss.oetiker.ch/rrdtool/doc/rrdgraph_data.en.html#IVDEF
> http://oss.oetiker.ch/rrdtool/doc/rrdgraph_data.en.html#ICDEF
>
> CDEF and DEF, are series of values, number of value depends on step
> parameter an the consolidation function (/CF/).
> VDEF is a single value.
>
> You cant use CDEF without DEF or CDEF variables because you can't
> calculate number of value needed for series.
>
> Le 21/02/2013 22:37, Alex van den Bogaerdt a écrit :
>>> I was trying to do something which I thought was fairly simple, but I
>>> keep on getting the following error:
>>>
>>> "ERROR: rpn expressions without DEF or CDEF variables are not supported"
>>>
>>> In the most simplest form, I am trying to do the following:
>>>
>>> DEF:A=<rrdfile>:A:AVERAGE
>>> DEF:B=<rrdfile>:B:AVERAGE
>>>
>>> VDEF:TA=A,TOTAL
>>> VDEF:TB=B,TOTAL
>>>
>>> CDEF:TAB=TA,TB,ADDNAN
>>>
>>> So, a VDEF is a set of data and a CDEF is a single value, but a TOTAL
>>> will be a single value?
>> VDEF support is currently very limited. What you are trying to do is,
>> indeed, not possible this way.
>>
>>> I am trying to take two totals and add them together - seems fairly
>>> common to want to do this?
>> The workaround is to do your math inside a CDEF, and then find the total.
>>
>> CDEF:c=a,b,ADDNAN
>> VDEF:total=c,TOTAL
>>
>> hth
>> alex
>>
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>
>